getting list and list element name for a nested list in R

Question

I made a nested list like the one below.

group1 <- list(color = c("red", "green", "blue"),taste = c("sweet", "sour"))
group2 <- list(color = c("orange","purple","yellow"),taste = c("tan", "salt"))
nestedlist <- list(group1, group2)

now from this "nested list", i want to find out the which group an element belongs and which list element it belongs. Pardon my lack of understanding with list structure.

For example

test <- c("red", "tan")

given test i want the return of "color" "group1" and "taste" "group2"..

Is there any function to do this? I struggle with lists often. any help would be appreciated

have you tried nestedlist <- list(g1 = group1, g2 = group2) instead of nestedlist <- list(group1, group2) ? This way, you can just do unlist(nestedlist) and search on that. — Aramis7d
– Aramis7d, Commented Aug 2, 2017 at 5:32
Fair point about the names, but it can become difficult when you have nestedlist <- list(g2.g1 = group1, g2 = group2) for instance. — thelatemail
– thelatemail, Commented Aug 2, 2017 at 5:43

Andrew Gustar · Accepted Answer · 2017-08-02 06:15:30Z

2

Here is another way to do it...

names(nestedlist) <- paste0("Group",1:length(nestedlist)) #add names to list
lookup <- unlist(nestedlist) #unlist, retaining names
names(lookup)[match(test,lookup)] #lookup matching names

[1] "Group1.color1" "Group2.taste1"

answered Aug 2, 2017 at 6:15

Andrew Gustar

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Florian · Accepted Answer · 2017-08-02 06:21:11Z

2

Here is a possible solution:

dat = lapply(test,function(z){sapply(nestedlist,function(x) 
                                        {sapply(x,function(y) {z %in% y})})})
do.call(rbind,lapply(dat, function(x) {c(group = which(sapply(x,any)),
                                 col = names(which(x[[which(sapply(x,any))]])))}))

Output:

     group col     
[1,] "1"   "color" 
[2,] "2"   "taste"

It also works if one group has more nested lists than the other, which was what I struggled with initially. Curious to see the solution of others, hope this helps!

edited Aug 2, 2017 at 6:21

answered Aug 2, 2017 at 5:54

Florian

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1 Comment

duvvurum Over a year ago

I am getting below error: Error in x[[which(sapply(x, any))]] : attempt to select more than one element in vectorIndex

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